Slated to attend and answer questions are representatives from the Pennsylvania Public Utility Commission, Pennsylvania Office of Consumer Advocate, PPL and FirstEnergy's Metropolitan Edison.

Consumers in Pennsylvania filed more than 1,500 billing complaints since the start of the year with the Public Utility Commission. Most of the complaints are about electric bills from variable-rate plans, some of which shot up 300 percent as a result of high demand and transmission issues in the middle of a harsh winter.

Pennsylvania's electricity marketplace was born in 1996, when state lawmakers started deregulating the industry. They had determined electricity bills in Pennsylvania were much higher than the national average.

By 2000, all of the state's residents were able to leave their so-called default utility and shop around for an electricity supplier. Default service providers are the regulated companies that own and operate delivery infrastructure. Prior to the competitive marketplace, they were the only companies able to sell electricity to consumers.

But the marketplace almost disappeared shortly after its introduction.

In exchange for provisions that allowed default utilities to recover costs associated with any infrastructure improvements they made, Pennsylvania lawmakers introduced rate caps on those companies. That made their lower prices much more appetizing than the competitive suppliers. Consumer interest in leaving default companies was so low that most competitive suppliers abandoned the marketplace altogether.

But most of those rate caps expired in 2010, allowing default utilities to raise rates. Then, the competitive suppliers returned.

At this point, 39.3 percent of all Pennsylvania electricity customers -- 2.2 million accounts -- have switched from their default service provider to a competitive supplier. Those customers account for 65.4 percent of all electricity load in the state.

The Pittsburgh Post-Gazette, through The Associated Press, contributed to this report.